Đề Read và Listen được học tro review là khá khó cho đợt này. Mặc dù đề Write dễ hơn đợt trước rất nhiều (đề Writing ngày 13/ 6/ 2019).Read More
Hôm nay mình kiếm được tận 2 bài Reading nhé – tải PDF
Copy your neighbor
THERE’S no animal that symbolizes rainforest diversity quite as spectacularly as the tropical butterfly. Any one lucky enough to see these creatures flitting between patches of sunlight cannot fail to be impressed by the variety of their patterns. But why do they display such colourful exuberance? Until recently, this was almost as pertinent a question as it had been when the 19th-century naturalists, armed only with butterfly nets and insatiable curiosity, battled through the rainforests. These early explorers soon realised that although some of the butter flies’ bright colours are there to attract a mate, others are warning signals. They send outa message to any predators: “Keep off, we’re poisonous.” And because wearing certain patterns affords protection, other species copy them. Biologists use the term “mimicry rings” for these clusters of impostors and their evolutionary idol.
But here’s the conundrum. “Classical mimicry theory says that only a single ring should be found in any one area,”explains George Beccaloni of the Natural History Museum, London. The ideais that in each locality there should be just the one pattern that best protects its wearers. Predators would quickly learn to avoid it and eventually all mimetic species in a region should converge upon it.
Sometimes ideas just pop up out of the blue. Or in Charlie Paton’s case, out of the rain. “I was in a bus in Morocco traveling through the desert,” he remembers. “It had been raining and the bus was full of hot, wet people. The windows steamed up and I went to sleep with a towel against the glass. When I woke, the thing was soaking wet. I had to wring it out. And it set me thinking. Why was it so wet?”
The answer, of course, was condensation. Back home in London, a physicist friend, Philip Davies, explained that the glass, chilled by the rain outside, had cooled the hot humid air inside the bus below its dew point, causing droplets of water to form on the inside of the window. Intrigued, Paton-a lighting engineer by profession-started rigging up his own equipment. “I made my own solar stills. It occurred to me that you might be able to produce water in this way in the desert, simply by cooling the air. I wondered whether you could make enough to irrigate fields and grow crops.”